We have tried you to make a walk through
the Collection Framework. The Collection
Framework provides a well-designed
set if interface and classes for sorting
and manipulating groups of data as
a single unit, a collection.

The
Collection Framework provides a standard
programming interface to many of the
most common abstractions, without
burdening the programmer with too
many procedures and interfaces.

The
Collection Framework is made up of
a set of interfaces for working with
the groups of objects. The different
interfaces describe the different
types of groups. For the most part,
once you understand the interfaces,
you understand the framework. While
you always need to create specific,
implementations of the interfaces,
access to the actual collection should
be restricted to the use of the interface
methods, thus allowing you to change
the underlying data structure, without
altering the rest of your code.

In
the Collections Framework, the interfaces
Map and Collection are distinct with
no lineage in the hierarchy. The typical
application of map is to provide access
to values stored by keys.

When
designing software with the Collection
Framework, it is useful to remember
the following hierarchical relationship
of the four basic interfaces of the
framework.

The
Collection interface is a
group of objects, with duplicates
allowed.

The
historical collection classes are
called such because they have been
around since 1.0 release of the java
class libraries. If you are moving
from historical collection to the
new framework classes, one of the
primary differences is that all operations
are synchronized with the new classes.
While you can add synchronization
to the new classes, you cannot remove
from the old.